There have been many efforts to provide improved combinations of physical properties in carbonate polymers and other engineering thermoplastic resins. For example, in U.S. Pat. No. 4,708,994 it is taught to incorporate reactive arylcyclobutene groups by means of alkylating or acylating aromatic groups of such resins with a molecule containing a reactive arylcyclobutene moiety to provide pendant arylcyclobutene moieties randomly along the polymer backbone. Such resins are then crosslinked and cured during a subsequent heating step and shown to be more solvent and heat resistant. Unfortunately, however, these materials having random and uncontrolled crosslinking throughout the polymer backbone are found to possess generally unsatisfactory combinations of other physical properties such as toughness.
In U.S. Pat. Nos. 4,795,827 and 4,825,001 cyclobutarene ketoaniline monomers are used for attaching cyclobutarene groups to polymers or other molecules having amino-reactive functionalities. However, no arylcyclobutene terminated carbonate polymer compositions are shown. Moreover, carbonate polymers endcapped or terminated with such monomers would not be sufficiently stable for typical engineering thermoplastic applications due to the known thermal instability of the carbamate linkage that would be produced.